001/*002 * Licensed to the Apache Software Foundation (ASF) under one003 * or more contributor license agreements. See the NOTICE file004 * distributed with this work for additional information005 * regarding copyright ownership. The ASF licenses this file006 * to you under the Apache License, Version 2.0 (the007 * "License"); you may not use this file except in compliance008 * with the License. You may obtain a copy of the License at009 *010 * http://www.apache.org/licenses/LICENSE-2.0011 *012 * Unless required by applicable law or agreed to in writing, software013 * distributed under the License is distributed on an "AS IS" BASIS,014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.015 * See the License for the specific language governing permissions and016 * limitations under the License.017 */018019package org.apache.hadoop.service;020021import org.apache.commons.logging.Log;022import org.apache.commons.logging.LogFactory;023import org.apache.hadoop.classification.InterfaceAudience.Public;024import org.apache.hadoop.classification.InterfaceStability.Evolving;025026/**027 * This is a state change listener that logs events at INFO level028 */029@Public030@Evolving031public class LoggingStateChangeListener implements ServiceStateChangeListener {032033 private static final Log LOG = LogFactory.getLog(LoggingStateChangeListener.class);034035 private final Log log;036037 /**038 * Log events to the given log039 * @param log destination for events040 */041 public LoggingStateChangeListener(Log log) {042 //force an NPE if a null log came in043 log.isDebugEnabled();044 this.log = log;045 }046047 /**048 * Log events to the static log for this class049 */050 public LoggingStateChangeListener() {051 this(LOG);052 }053054 /**055 * Callback for a state change event: log it056 * @param service the service that has changed.057 */058 @Override059 public void stateChanged(Service service) {060 log.info("Entry to state " + service.getServiceState()061 + " for " + service.getName());062 }063}